Vacuum electric tube



May 7 929 E. Y. ROBINSON 1,712,402

VACUUM ELECTRIC TUBE 'Filed June 2, 1924 Patented May 7, 1929.

UNITED STATES PATENT OFFICE.

ERNEST YEOMAN ROBINSON, 0F WITHINGTON, MANCHESTER, ENGLAND, ASSIGNOB TO METROPOLITAN-VICKEBS ELECTRICAL COMPANY LIMITED, 0F LONDON, ENG'- LAND, A BRITISH JOINT-STOCK COMPANY.

VACUUM ELECTRIC TUBE.

Application led June 2, 1924, Serial No. 717,326', and in Great Britain Jlne` 14, 1923.

This invention relates to vacuum electric tubes containing cathodes which are heated for example by a thermionic bombardment or by radiation from a heated auxiliary member such as a filament or by high frequency electromagnetic induction and which are of sheet material in flat or tubular form. The object of the invention is an improved method of supporting such cathodes and leading in the current thereto.

According to this invention it is arranged that one or more sheets or tubes comprisiner the cathode are supported by a plurality o supports such for example as stems and moreover are preferably supported on a plurality of sides. In this manner the cathode may be rigidly fixed with respect to other electrodes of the device.

Furthermore, the cathode supports whilst capable of movement in a longitudinal direction are fixed in other directions so that expansion thereof is permitted.

The supporting stems may be employed as electrical leads to the cathode.

rllhis method of supporting and constructing the cathode has several advantages. Firstly, the cathode or cathode portions are supported more rigidly and the electrodes may therefore be given a small separation; secondly, where the cathode is of the type described in the specification of my copending application Serial No. 653,544; filed 24th July 1923 the cathode portions may be spaced from each other by means of spacing pieces inserted between the supporting stems and either fixed thereto or arranged to be in sliding contact therewith; thir ly the plurality of leadin -in wires to the cathode and the spacing o these round the cathode edges results in a more uniform distribution of current in the cathode sheet or tube and thus promotes more uniform heating; fourthly, it becomes necessary when cathodes of large emission surface are employed to use a plurality of leads connected to the cathode to prevent overheating of the lead-in wires.

In the accompanying drawing Fig. 1 represents a section taken axially or longitudinally through a cathode structure embodying the present invention; and

Fig. 2 is a detail perspective view of one of the members of the cathode structure shown in Fig. 1.

Referring to Fig. 1, the cathode structure therein illustrated is adapted for use, for example, 1n a tube of the type set forth in the specification of my copending application Serlal N o. 603,715 filed 27th November, 1922.

In the construction shown in Figs. 1 and 2 the cathode is of the type described in my copending application berial No. 653,544: hereinbefore referred to, it comprising an outer tube 3, an inner tube 15 and a starting filament 16. The two tubes 3 and 15 are provided with perforations 87 formed near the ends of the tubes. The two tubes 3 and 15 are mounted with respect to and insulated from one another by means of steatite bushes 88 and 89. Each brush comprises two cylindrical portions of different diameter, as clearly shown. The inner tube 15 iits upon the smaller portions of the bushesand is attached thereto by means of set screws 90. The outer tube 3 is of greater length than the inner tube 15 and is attached to the upper bush 88 by means of set screws 91 whilst the lower end of the tube slides freely upon the larger portion of the bush 89. The upper end 92 of the outer tube 3 extends beyond the bush 88 and is connected by means of the arms 45 to a clamp or the like by means of which it can be secured, for example, to a re-entrant portion of the tube envelope. The arms 45 may constitute thev lead-in conductor for the outer tube 3. A. lead-in conductor 93 passes through the upper bush 88 and is connected by means of a nickel or other conductor 94 to one of the circumferentially spaced arms or strips formed by the portions 95 of the tube intervening between the longitudinal slots or perforations 87. Such arms or strips 95, it will be appreciated, constitute a plurality of supports at both ends of the cathode tubes and they also constitute a plurality of leadin conductors for said tubes at the upper end thereof as these strips are all connected electrically by the upper terminals of the respective tubes. The starting filament 16 is connected to the lead-in conductors 23 and 24 which pass through the upper bush 88. The bight of the filament 16 is engaged by a hook 31 attached to a rod 96 which carries the shield 4 and passes through the lower bush 89 being retained therein by two abutments 97 welded to the rod.

The cathode tubes 3 and 15 are formed of metal having a comparatively low melting point. For example they may consist of steel, iron, nickel or molybdenum and are coated on their active siu'faces, that is to say on the portions which are dis between the perforations 87, with a substance such as a mixture of baiium andstrontiuin oxides for facilitating emission of electrons. Such coatin may be applied in any suitable manner suc for example as that set forth iii the ification of my copending application rial No. 715,653 tiled May 24, 1924. Since the tubes are not coated at their ends these portions will remain inactive and therefore will eli'ectively confine the space current to the interelectrode space. The cathode may be mounted within an anode. The starting cathode 16 may be a tungsten lanient or an oxide coated filament and v adapted to heat the inner tube 15 by electronic bombardment or heat radiation as the case may be.

Although one s )ecific construction has been illustrated an described it will be unl dei-stood that the invention is not limited to same since various modifications may be made without departing fi-oiii the scope of the invention.

I claim as my invention 1. Cathode means for a vacuum-electric tube comprising a sheet metal cathode, an auxiliary member for heating said sheet ineta-l cathode by transference of energy thereto, a plurality of parallel-connected strips formed integrally with said sheet metal cathode at a plurality of distributed points at both ends thereof, and a single terminal conductor connected to said strips.

2. Cathode means for a vacuum electric tube comprising a sheet metal cathode adapted to be heated by the transference of energy to it, for causing it to emit electrons,v

and having a plurality of strips formed integrally with it at a plurality of distributed points, and a supporting member, said strips eing carried movably upon said supporting member so that the cathode can expand without distortion thereof.

3. Cathode means for a vacuum electric tube comprising a sheet metal cathode adapted to be heated by the transference of energy to it, for causing it to emit electrons, and having a plurality of strips formed integrally with it at a plurality of distributed points, and a supporting member, said strips being slidable upon said supportin member to permit expansion of the catho e without distortion thereof.

4. Cathode means for a vacuum electric tube comprising a sheet metal cathode having an electron-emitting portion and a plurality of strips integral with said electroneinitting portion and extending therefrom at a plurality of distributed points.

5. Cathode means for a vacuum electric tube comprising a sheet metal cathode having an electron-emitting portion and, at each end thereof, a plurality of strips integral with said electron-emitting portion and extending tlierefroiii at a plurality of distributed poiiits.

6. Cathode means for a vacuum electric tube comprising a sheet metal cathode havin an electron-emitting portion and a plura ity of strips formed integrally with said electro -emitting portion and extending therefroml at a plurality o f distributed points, and a terminal conductor to which strips aie electrically connected in para e 7. Cathode means for a vacuum electric tube comprising a sheet metal cathode having an electron-emitting portion and, It each end thereof, a plurality of strips integral with said electron-emitting portion and extending therefrom at a plurality of distributed points, and a terminal conductor to which said strips are electrically connected in parallel.

8. Cathode means for a vacuum electric tube comprising a tubular sheet metal cathode having, at one end at least, a plurality of strips integral therewith and terminating in a single terminal member.

.9. Cathode means for a vacuum electric tube comprising a tubular sheet metal cathode having, at one end at least, a plurality of eylindrically disposed strips fomned interally therewith and terminating in a meinr which has the forni of a. cylindrical collar.

10. Cathode means for a vacuum electric tube comprising a tubular sheet metal cathode having, at one end at least, a. plurality of eylindrically disposed strips formed integrally therewith and terminating in a member having the form of a cylindrical collar, and an internally disposed auxiliary member for heating said cathode by transference of energy thereto.

11. Cathode means for a vacuum electric tube comprising a tubular sheet metal cathode havin", at one end at least, a plurality of eylindrically disposed strips formed integrally therewith and terminatin in a member which has the form of a cylindrical collar, and an internally dis osed auxiliary member for heating said cat ode by transference of energy thereto, said auxiliary member embodying a tubular sheet metal element having, at one end at least, a plurality of eylindrically dis osed strips formed integrally therewith an terminating in a member which has the form of a cylindrical collar.

' 12. Cathode means for a vacuum electric tube comprising a cylindrical sheet metal cathode, an internally disposed c lindrical auxiliary member for heating sai cathode by transference of energy thereto, said cathode and auxiliary member being slotted 5 drical portions of different diameters which portions respectively receive the ends of said cathode and said auxiliary member and /support them relative to Aone another.

13. Cathode means for a vacuum electric 1o tube comprising a cylindrical sheet metal cathode, an internally disposed cylindrical auxiliary member for heating said cathode by transference of energy thereto, the cathode and auxiliary member havingl circum- 15 ferentially spaced strips formed integrally therewith and terminating in cylindrical collars, a bush of insulating and heat resisting material providedwith c lindrical ortions of different diameters which respective] receive the cylindrical collars of said cat ode and said auxiliary member and support them relatively to one another, and an element within said auxiliary member which is capable of being heated by passage of an electric current through it and is supported by said bush.

In testimony whereof I have subscribed my name this ninth day of May, 1924.

ERNEST' YEOMAN ROBINSON. 

